Desorption of tetracycline from montmorillonite by aluminum, calcium, and sodium: an indication of intercalation stability

Abstract

As the uptake of cationic drugs, such as tetracycline (TC), was attributed to cation exchange, the stability of adsorbed TC on a Ca-montmorillonite SAz-2 was studied using cationic solutions of different valence charges under different pH conditions. At the initial loading of 356 mg g -1 , the amounts of TC desorbed by 0.05 M AlCl 3 , CaCl 2 , and NaCl were 133 ± 4, 83 ± 6, and 50 ± 4 mg g -1 , respectively, or 37, 23, and 14 %. However, when the amount or percentage of TC desorbed was normalized to the equivalence of each cation, the values were in the range of 44-50 mg g -1 or 11-14 % per 10 mmol of charge. The kinetics of TC desorption were moderately fast and almost reached equilibrium in 6 h. The results followed the pseudo-second-order kinetic model with reaction rate in the order of AlCl 3 [ CaCl 2 [ NaCl at a higher initial TC loading level. The total amount of TC desorbed after five desorption cycles followed the order of AlCl 3 [ CaCl 2 [ NaCl, too, suggesting that cations with higher positive charges, thus, less hydrated, are preferred to remove adsorbed cationic drugs. The FTIR analyses showed larger band shift when Al 3? was used as the desorbing reagent. The XRD patterns before and after TC desorption revealed no changes in basal spacing, even after five desorption cycles, suggesting that the removal of TC from SAz-2 was largely from the external surfaces.

Effects of the pH and anions on the adsorption of tetracycline on iron-montmorillonite

“…Similar to many previous studies (Myers et al, 1983;Kulshrestha et al, 2004;Chang et al, 2014), the FTIR spectra of TC in Fig. 9 indicate that the band positions of several characteristic peaks in the recorded region changed once TC was adsorbed onto Fe-Mt, while no change occurred for the band centered at 1456 cm −1 , which can be ascribed to the C_C skeleton in ring-A.…”

“…Thus, it is deduced that most of the TC adsorption occurs outside the Mt counterpart particles in FeMt, with which certain surface complexes of TC are thus formed. Chang et al (2014) reported that the XRD patterns of Ca 2+ -Mt revealed no change in the basal spacings before and after TC desorption by using Al 3+ , Ca 2+ and Na + cations, suggesting that the TC retention is largely distributed on the external surfaces. This is mainly because both the -CONH 2 group in TC 1 and -OH group in TC 2 can directly bind to those negative surface sites via a 'cation-bridging' interaction (MacKay and Canterbury, 2005).…”

Removal of tetracycline antibiotics from aqueous solution by amino-Fe (III) functionalized SBA15

“…The band at 1614 cm −1 shifted to a higher frequency, indicating that the carbonyl groups or the amid-NH in ring A may have been influenced by the complexation of TCs and Fe (III) on the sorbent. This was consistent with the complexation of TC and hydrous oxides of Al, Fe [2,31]. The intensity of the 1581 cm −1 band decreased, and the slight shift of the 1455 cm −1 band indicated that carbonyl groups of ring C or amid-NH in ring A of the TCs may form complexes with Fe (III) on the sorbent.…”

“…5a) followed the study of Gu et al and Chang et al [2,31]. The 1672 and 1523 cm −1 bands were assigned to the carbonyl and amino groups of the amide in ring A, respectively.…”

Efficient adsorption removal of tetracycline by layered carbon particles prepared from seaweed biomass

“…As such, a series of adsorbents including natural and synthetic materials such as montmorillonite , carbon nanotubes , Fe‐OMC‐100 , Fe‐Mn binary oxide , and MnFe 2 O 4 /activated carbon magnetic composites have been employed for the removal of tetracycline from water. Among these adsorbents, the biosorbents are believed to be promising on the basis of their low cost, high adsorption efficiency and wide availabilities .…”